1985 318i Will Not Idle Properly (HELP!)

I recently aquired a 1985 BMW 318i. It will not idle properly. When the engine is not in gear and in motion it will jump constantly between 900 and 1100 RPMs. Everything else seems to be running properly. I've
been told by some that the idle control unit needs to be replaced. Is this likely? I have heard also that there is an idle control valve; this is not the problem? I cannot locate the idle control unit. Someone told me that it is between the glove box and dash, but I can't find it. Will someone provide me with detailed instructions or a diagram? I cannot afford a mechanic and am not savvy with cars. I cannot afford a manual, but wonder whether or not this information is provided in the Bentley manual.
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If you cannot afford a manual you cannot afford $200 for a new idle control unit, which is visible after removing the glovebox.
It is possible to disconnect this automatic idle feature entirely and set a curb idle using the throttle cable adjustment, although starting and warmup would then require holding the gas pedal down.
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How do I disconnect the automatic idle feature? I removed the cover between in-between the dash and glove box. I moved the hardware in and out of position several times while looking for the idle control unit. All of the sudden, the car started idling properly, steady at 600 or 700 RPMs. This is a coincidence? Or did I disconnect something by mistake? I still have a problem? What do you think it is? I cannot afford an extram $50 for a manual and thought that I could obtain an ICU for $50 at pick-your-part yard.
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All 318i's have this problem eventually, so used is not advised.
Maybe you have a wiring problem. The ICU is a small black box, literally above the glovebox. See http://www.realoem.com/bmw/select.do
Now that I think about, disconnecting is a little involved. You must block all flow thru the silver cylinder located engine top center. It has a two-pin connector on the back. Remove the back hose, tape a penny over the opening, and reassemble, leaving the connector off.
Having blocked this air valve, you must now adjust the throttle cable to keep the throttle from fully closing. Turn the nut on the bracket thru which the cable passes until the engines idles at about 750 RPM when fully warm.

keep it from stalling during warmup.
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wrote:

My thought is that if he couldn't afford the $50 or so (kinda high if you ask me) and he isn't car savvy as he put it, why in the world did he bother with an older car, much less a BMW.
That being said, first place I would've looked would have been a vacuum leak (cracked hoses). I've found plenty of then on my sin's 87 325is and my 89 325i...
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